Project Summary/Abstract Often, the complex mechanisms of the hand are damaged either by trauma or neurological disorder. In this event, surgical intervention is necessary to restore or partially restore normal hand function. Current surgical intervention is based on years of prior trial and error outcomes. Currently there is not a tool for surgeons to predict the outcomes of new techniques. The long-term objective of this project is to advance tendon reconstructive surgery, by providing a new way to predict the surgical outcomes using a virtual model for surgeons to examine the outcomes of surgery like range of motion and strength of grip. A physical robotic representation of the hand tendon system would also be useful for providing a way to perform the surgery without stepping into the operating room. This proposal seeks to take the first step towards the broader project objective, by examining the feasibility of using a virtual model and a robotic testbed to simulate two specific tendon surgeries. The first surgery will be the flexor tendon repair surgery that seeks to reconnect severed flexor tendons. Often during this surgery, the tendon will be shortened. This shortening can lead to different results depending on the length shortened. This study will seek to replicate these effects both virtually and robotically. The second surgery will be the FDS Opponensplasty tendon transfer. This surgery seeks to restore the opposition function of the thumb by donating a tendon from the FDS tendon from one finger and rerouting it in the palm to connect to the thumb. This surgery has many variables and many different methods. Successfully simulating these surgeries will demonstrate the virtual model and robotic testbeds utility for future unexplored surgical techniques. The specific aims of this proposal are: 1. Expand robotic testbed and virtual model to include thumb tendon system. 2. Simulate reconstructive tendon surgeries using the robotic and virtual digits 3. Simulate reconstructive tendon surgeries using cadavers and virtual digits. Using the PI?s current virtual model framework and robotic testbed as starting points, a thumb will be added to both model and tested. Using the new two digit model and testbed each of the surgeries will be simulated to demonstrate their accuracy at mimicking the outcomes of reconstructive tendon surgeries. A robotic testbed will promote rigorous and repeatable results. The model will also be compared to cadaver simulation of the surgery to demonstrate the model?s translation to true biological systems. The use of a cadaver while being more anatomically correct, will deteriorate and change over the time of experimentation.